title: Characteristics of cases with unknown stage prostate cancer in a population-based cancer registry.
abstract: BACKGROUND
  The New South Wales Central Cancer Registry (NSW CCR) is the only population-based cancer registry in Australia that has routinely collected summary stage at diagnosis since its inception in 1972. However, a large proportion of prostate cancer cases have "unknown" stage recorded by the registry. We investigated the characteristics of prostate cancer cases with "unknown" stage recorded by the NSW CCR, and examined survival for this group.
  
  
  METHODS
  Data were obtained from the NSW CCR for all first primary prostate cancer cases diagnosed in 1999-2007. Summary stage was recorded as localised, regional, distant or "unknown". Associations between disease stage and patient characteristics (age, place of residence at diagnosis, year of diagnosis and country of birth) and prostate cancer specific survival were investigated using multivariable logistic regression and Cox proportional hazards models respectively.
  
  
  RESULTS
  Of 39852 prostate cancer cases, 41.8% had "unknown" stage recorded by the NSW CCR. This proportion decreased significantly over time, increased with increasing age at diagnosis and was higher for those living in socio-economically disadvantaged areas. The proportion with "unknown" stage varied across area health services. Prostate cancer specific survival for cases with "unknown" stage was significantly poorer than for those with localised stage but better than for those with regional or distant stage.
  
  
  CONCLUSIONS
  Researchers or others using cancer registry stage data to examine prostate cancer outcomes need to consider the differences between cases with "unknown" stage at diagnosis and those with known stage recorded by the registry, and what impact this may have on their results.
authors.affiliation: Cancer Research Division, Cancer Council New South Wales, P.O. Box 572, Kings Cross, NSW 1340, Australia; Sydney School of Public Health, University of Sydney, NSW 2006, Australia. Electronic address: qingweil@nswcc.org.au.
authors.forename: Qingwei
authors.initials: Q
authors.lastname: Luo
authors.forename: Xue Qin
authors.initials: XQ
authors.lastname: Yu
authors.forename: Claire
authors.initials: C
authors.lastname: Cooke-Yarborough
authors.forename: David P
authors.initials: DP
authors.lastname: Smith
authors.forename: Dianne L
authors.initials: DL
authors.lastname: O'Connell
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D009517:New South Wales / Q000453:epidemiology; D011379:Prognosis; D011471:Prostatic Neoplasms / Q000453:epidemiology* / Q000473:pathology* / Q000601:surgery; D012042:Registries / Q000706:statistics & numerical data*; D012959:Socioeconomic Factors; D055815:Young Adult
keywords: Australia; Bias; Cancer registry; Epidemiology; PSA (prostate-specific antigen) test; Population-based; Prostate cancer; Socio-economic status; Survival; Unknown stage